1. Field of the Invention:
The present invention generally relates to a thermal expansion valve. More particularly, the present invention relates to a thermal expansion valve, for use in a refrigerating cycle, which expands refrigerant flowing thereinto from a high-pressure side liquid refrigerant circuit by reducing the pressure of such refrigerant according to the overheat of refrigerant at the outlet of an evaporator, and is preferably applied to, for example, a thermal expansion valve used for an automotive air conditioning system.
2. Description of Related Art:
Conventionally, as this type of thermal expansion valve, a thermal expansion valve, in which a thermosensitive element part for sensing the temperature of the refrigerant at the exit of an evaporator is incorporated in a housing in addition to a built-in expansion mechanism part, has been known, as disclosed in the Japanese Unexamined Patent publication No. Hei 6-26741.
The thermosensitive element part is fixed to the housing. On the other hand, the valve element of the expansion mechanism is operated in response to the displacement of a diaphragm provided within the case of the thermosensitive element.
As a result of experiments and examination by the inventors of the present invention, it was found that noise had been caused by the following reason due to the operation of the expansion valve:
The valve element of the expansion mechanism adjusts an opening of a throttle passage which sharply reduces high-pressure liquid refrigerant flowing thereinto from a high-pressure side liquid refrigerant circuit and thereby expands the refrigerant. Therefore, the valve element repeats a minute vibration by an influenced of the sharp pressure reduction and expansion of the refrigerant within the throttle passage.
The vibration of the valve element transmits to the housing though a valve stem linked to the valve element, a metallic contacting member in contact with the valve stem, the metallic diaphragm in contact with the contacting member, and a case of the thermoelement, for fixedly holding the outer circumferential portion of the diaphragm.
Therefore, it turns out that the noise caused by the vibration of the valve element is released to the outside via the housing, a refrigerant piping connected to the housing, and other components.